1. Field of the Invention
The present invention relates to a substrate comprising magnetoresistive elements exhibiting a magnetoresistive effect, and a monitor element which is formed in the same structure as the magnetoresistive elements, for measuring the direct-current resistance value of the magnetoresistive element, wherein the structure of gap layers formed on and below the monitor element is improved to prevent a short circuit of the monitor element in measurement of direct-current resistance. The present invention also relates to a method of manufacturing the substrate, and a method of processing the substrate.
2. Description of the Related Art
FIG. 34 is a partial sectional view of a conventional substrate comprising magnetoresistive elements as viewed from the ABS side.
As shown in FIG. 34, a base insulating layer 13 made of Al2O3 is formed on a substrate 1 made of, for example, Al2O3xe2x80x94TiC (alumina-titanium carbide). A lower shielding layer 12 made of a magnetic material such as an NiFe alloy or the like is formed on the base insulating layer 13, and a lower gap layer 3 made of an insulating material such as Al2O3 or the like is formed on the lower shielding layer 12.
Referring to FIG. 34, a plurality of magnetoresistive elements 4 and a monitor element 5 are formed in a line in the ABS direction (the X direction shown in the drawing) on the lower gap layer 3 (the drawing does not show an inductive head).
In FIG. 34, a multilayer film 6 comprising a spin valve film (a GMR element), for example, composed of an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer is formed at the center of each of the magnetoresistive elements 4. The pin valve film serves as an element using the giant magnetoresistive effect so that electric resistance changes with changes in a leakage magnetic field from a recording medium to detect recording signals. As shown in FIG. 34, electrode layers 7 made of a nonmagnetic metal material such as chromium (Cr) or the like are formed on both sides of the multilayer film 6.
The monitor element 5 is also formed in the same structure as the magnetoresistive elements 4. Namely, a multilayer film 8 exhibiting the magnetoresistive effect is formed at the center of the monitor element 5, and electrode layers 9 made of chromium (Cr) are formed on both sides of the multilayer film 8. The magnetoresistive elements 4 and the monitor element 5 are simultaneously formed on the lower gap layer 3 by pattering.
As shown in FIG. 34, an upper gap layer 10 made of an insulating material such as Al2O3 is formed on the magnetoresistive elements 4 and the monitor element 5, and an upper shielding layer 11 made of a NiFe alloy (permalloy) is further formed on the upper gap layer 10.
The monitor element 5 functions as a so-called processing monitor provided for setting a predetermined value of direct-current resistance (DCR) of the plurality of magnetoresistive elements 4 formed in alignment with the monitor element 5. After the monitor element 5 plays the role of the processing monitor, it is removed.
In order to set the direct-current resistance of the magnetoresistive elements 4 to the predetermined value, the ABS side (in the X direction shown in the drawing) of the magnetoresistive elements 4 and the monitor element 5 is ground (height setting), while measuring the direct-current resistance between the electrode layers 9 which constitute the monitor element 5. Then, when a predetermined direct-current valve is obtained, grinding of the ABS side is finished.
As described above, since the plurality of magnetoresistive elements 4 and the monitor element 5 have the same structure and are formed in a line parallel to the ABS side, the magnetoresistive elements 4 and the monitor element 5 have the same dimension in the height direction (the Y direction shown in FIG. 34). Therefore, the plurality of magnetoresistive elements 4 and the monitor element 5 can be set to the same direct-current resistance value by grinding the ABS side.
Namely, when the direct-current resistance of the monitor element 5 reaches a predetermined value by grinding, the direct-current resistance of the magnetoresistive elements also reaches the predetermined value.
However, in grinding the ABS side of the magnetoresistive elements 4 and the monitor element 5 while measuring the direct-current resistance between the electrode layers 9 which constitute the monitor element 5, the shielding layers 11 and 12 and the-electrode layers 9, which are exposed from the ABS side, cause smearing (sags) to cause electrical contact between the electrode layers 7 and the shielding layers 11 and 12, thereby short-circuiting the electrode layers 7 and the shielding layers 11 and 12.
For example, where sags 12a occur in the lower shielding layer 12 formed below the monitor element 5, as shown in FIG. 35, electrical connection occurs between the sags 12a and the electrode layers 9. As a result, the direct-current resistance (DCR) between the electrode layer 9 of the monitor element 5 cannot be precisely measured, and thus the dimensions of the magnetoresistive elements 4 in the height direction (the Y direction shown in FIG. 35) cannot be set to a value with which the direct-current resistances are a predetermined value.
Particularly, it is confirmed that the above problem significantly occurs when the gap length G1 determined by the thickness of the lower gap layer 3, and the gap length G2 determined by the thickness of the upper gap layer 10 are 700 angstroms or less.
In grinding the ABS side, sags 12a occur not only between the electrode layers 9 of the monitor element 5 and the shielding layers 11 and 12, but also in the electrode layers 7 of the magnetoresistive elements 4, and in the lower shielding layer 12 formed below the magnetoresistive elements 4, for example, as shown in FIG. 35, causing electrical connection between the electrode layers 7 of the magnetoresistive elements 4 and the shielding layer 12. However, after grinding is finished, the ABS side of the magnetoresistive elements 4 is lapped to remove the sags of the electrode layers 7 and the shielding layers 11 and 12, thereby maintaining an electrical insulation state between the electrode layers 7 of the magnetoresistive elements 4 and the shielding layers 11 and 12 in a magnetic head product.
The present invention has been achieved for solving the above problem, and an object of the present invention is to provide a substrate comprising magnetoresistive elements, which is capable of preventing a short circuit between electrode layers of a monitor element and shielding layers, and precisely measuring direct-current resistance during height setting processing, a method of manufacturing the substrate, and a method of processing the substrate.
The present invention provides a substrate comprising a lower shielding layer formed on the substrate, a lower gap layer formed on the lower shielding layer, a plurality of magnetoresistive elements each comprising a multilayer film exhibiting the magnetoresistive effect and electrode layers conducting to the multilayer film, and a processing monitor element having substantially the same structure as the magnetoresistive elements, these elements being arranged in a line on the lower gap layer, wherein besides the lower gap layer, an insulating layer is formed between the monitor element and the lower shielding layer to be exposed from the ABS side so that the distance between the monitor element and the lower shield layer exposed from the ABS side is larger than the distance between the magnetoresistive elements and the lower shield layer exposed from the ABS side.
In the present invention, the total thickness of the lower gap layer and the insulating-layer is preferably 700 angstroms or more.
A typical structure of the substrate of the present invention preferably comprises the insulating layer formed on the lower shielding layer, the lower gap layer formed on the insulating layer, and the monitor element formed on the lower gap layer.
In a preferred example of such a structure, a recessed portion is formed in the surface of the lower shielding layer, an insulating layer is formed in the recessed portion, and the monitor element is formed on the insulating layer with the lower gap layer provided therebetween.
The surface of the insulating layer formed in the recessed portion of the lower shielding layer, and the surface of the lower shielding layer are preferably formed in the same plane.
In the present invention, the insulating layer may formed on the surface of the lower shielding layer to form steps between the upper surface of the insulating layer and the surface of the lower shielding layer, so that inclined surfaces may be formed on the sides of the insulating layer in the stepped portions.
In the present invention, the insulating layer is preferably made of any one of insulating materials such as SiO2, Ta2O5, TiO, Al2O3, Si3N4, AlN, and WO3.
In the present invention, the insulating layer may also be formed below the electrode layers of the magnetoresistive elements in a region excluding portions below the multilayer films which respectively constitutes the magnetoresistive elements.
The present invention also provides a substrate comprising a lower shielding layer formed on the substrate, a lower gap layer formed on the lower shielding layer, a plurality of magnetoresistive elements each comprising a multilayer film exhibiting the magnetoresistive effect and electrode layers conducting to the multilayer film, and a processing monitor element having substantially the same structure as the magnetoresistive elements, these elements being arranged in a line on the lower gap layer, wherein besides an upper gap layer, an insulating layer is formed on the magnetoresistive elements and the monitor element to be exposed from the ABS side so that the distance between the monitor element and an upper shielding layer exposed from the ABS side is larger than the distance between the magnetoresistive elements and the upper shielding layer exposed from the ABS side.
In the present invention, the total thickness of the upper gap layer and the insulating layer is preferably 700 angstroms or more.
The insulating layer may also be formed on the electrode layers which constitute the magnetoresistive elements in a region excluding portions above the multilayer films which respectively constitute the magnetoresistive elements.
The insulating layer overlapped with the electrode layers of the magnetoresistive elements may be formed to be exposed from the ABS side.
The present invention further provides a method of manufacturing a substrate comprising magnetoresistive elements, the method comprising the steps of forming a lower shielding layer on the substrate, and then forming a lift off resist layer on the lower shielding layer; etching to a predetermined depth a portion of the surface of the lower shielding layer, on which the resist layer is not formed, to form a recessed portion in the surface of the lower shielding layer; forming an insulating layer in the recessed portion formed in the surface of the lower shielding layer and then removing the resist layer; forming a lower gap layer on the lower shielding layer and the insulating layer; and forming a plurality of magnetoresistive elements each comprising a multilayer film exhibiting the magnetoresistive effect and electrode layers conducting to the multilayer film on a portion of the lower gap layer on which the insulating layer is not formed, and a processing monitor element having substantially the same structure as the magnetoresistive elements on a portion of the lower gap layer on which the insulating layer is formed, so that these elements are arranged in a line.
In the present invention, the recessed portion formed in the surface of the lower shielding layer may also be formed in a portion where the electrode layers of the magnetoresistive elements are formed, so that after the insulating layer is formed in the recessed portions, the electrode layers of the magnetoresistive elements are formed on the lower gap layer overlapped with the insulating layer.
In the present invention, the recessed portions formed in the surface of the lower shielding layer are preferably formed below the electrode layers behind at least the multilayer films of the magnetoresistive elements.
The present invention further provides a method of manufacturing a substrate comprising magnetoresistive elements, the method comprising the steps of forming a lower shielding layer on the substrate, and then forming a insulating material layer on the lower shielding layer; forming a resist layer on the insulating material layer and etching off a portion of the insulating layer, which is not covered with the resist layer, to leave the insulating material layer below the resist layer as an insulating layer; removing the resist layer and forming a lower gap layer on the insulating layer and the lower shielding layer; and forming a plurality of magnetoresistive elements each comprising a multilayer film exhibiting the magnetoresistive effect and electrode layers conducting to the multilayer film on a portion the lower gap layer where the insulating layer is not formed, and a processing monitor element having substantially the same structure as the magnetoresistive elements on a portion of the lower gap layer where the insulating layer is formed, so that these elements are arranged in a line.
In the present invention, the insulating layer may also be formed below the electrode layers of the magnetoresistive elements, so that the electrode layers of the magnetoresistive elements are formed on the lower gap layer overlapped with the insulating layer.
In the present invention, the insulating layer formed below the electrode layers of the magnetoresistive elements may be exposed from the ABS side.
In the present invention, inclined surfaces are preferably formed on the sides of the insulating layer.
In the present invention, inclined surfaces are preferably formed on the sides of the insulating layer by isotropic etching.
Alternatively, the resist layer is formed on the insulating material layer, and then heat-treated to form inclined surfaces on the sides of the resist layer, and an inclined layer is preferably formed on the sides of the insulating layer left below the resist layer by isotropic etching.
In the present invention, the insulating material layer is preferably made of any one of insulating materials such as SiO2, Ta2O5, TiO, Al2O3, Si3N4, AlN, and WO3.
The present invention further provides a method of processing a substrate comprising magnetoresistive elements, the method comprising grinding the magnetoresistive elements and a monitor element from the ABS side in the height direction while measuring the direct-current resistance value between electrode layers of the monitor element until a predetermined direct-current resistance value is obtained.
IA magnetic head slider comprising a magnetoresistive element composed of a spin valve film (a GMR element) is formed, by various kinds of processing, from a wafer in which a plurality of magnetoresistive elements are formed.
The exposed surface of the magnetoresistive element formed in the slider is referred to as xe2x80x9cthe ABS sidexe2x80x9d, which is opposed to a recording medium in reproducing-signals from the recording medium. The direction perpendicular to the ABS side opposed to the recording medium, i.e., the direction away from the recording medium, is referred to as xe2x80x9cthe height directionxe2x80x9d. The length of the magnetoresistive element in the height direction is a very important dimension for determining the direct-current resistance of the magnetoresistive element.
In order to set the length of the magnetoresistive element in the height direction to a predetermined dimension by grinding (height setting processing) on the basis of the relation to the direct-current resistance, a monitor element having the same structure of the magnetoresistive element is formed in alignment with magnetoresistive elements formed on the substrate, and the ABS side of the magnetoresistive elements and the monitor element is subjected to height setting processing, while measuring the direct-current of the monitor element. At the time the predetermined direct-current resistance is obtained, height setting processing is finished to form the magnetoresistive elements each having a length in the height direction with the predetermined direct-current resistance.
However, at present, the thickness of each of the gap layers formed on and below the monitor layer decreases as the recording density increases, and thus smearing (sagging) occurs in the shielding layers formed on and below the gap layers to be exposed from the ABS side in height setting processing. There is thus the problem of causing a short circuit between the monitor element and the shielding layers on the ABS side during measurement of direct-current resistance.
Particularly, in height setting processing, the ABS side of the monitor element is ground in the direction from the lower shielding layer formed below the monitor element to the upper shielding layer formed above the monitor element, and the thickness of the lower gap layer formed below the monitor element is actually smaller than the thickness of the upper gap layer formed on the monitor element. Therefore, smearing in the lower shielding layer causes the great problem of readily producing electrical connection between the lower shielding layer and the monitor element on the ABS side.
Accordingly, in the present invention, besides the lower gap layer, an insulating layer is provided between the monitor element and the lower shielding layer to increase the space between the monitor element and the lower shielding layer, as compared with a conventional substrate, so that even when smearing occurs in the lower shielding layer exposed from the ABS side, the occurrence of electrical connection between the monitor element and the lower shielding layer can be prevented.
The present invention further provides a substrate comprising a lower shield layer formed on the substrate, a lower gap layer formed on the lower shield layer, a plurality of magnetoresistive elements formed on the lower gap layer and each comprising a multilayer film exhibiting the magnetoresistive effect, and electrode layers conducting to the multilayer film, and a processing monitor element formed adjacent to the plurality of magnetoresistive elements and having substantially the same structure as the magnetoresistive elements, wherein the monitor element is formed on a portion of the substrate where the lower shielding layer is not formed, with the lower gap layer formed between the monitor element and the substrate.
In the present invention, an insulating layer is preferably formed between the substrate and the lower gap layer formed below the monitor element.
The surfaces of the insulating layer and the lower shielding layer are preferably formed in the same plane.
In the present invention, an upper shielding layer formed on the magnetoresistive elements with an upper gap layer provided therebetween is preferably not formed on a portion of the upper gap layer which is formed on the monitor element.
In the present invention, a write gap layer of an inductive head is preferably formed on the upper gap layer formed on the monitor element.
The present invention further provides a method of manufacturing a substrate comprising magnetoresistive elements, the method comprising the steps of forming a lower shielding layer on the substrate and then forming a lower gap layer on the lower shielding layer and the substrate on which the lower shielding layer is not formed; and forming a plurality of magnetoresistive elements each comprising a multilayer film exhibiting the magnetoresistive effect and electrode layers conducting to the multilayer film on a portion of the lower gap layer where the lower shielding layer is formed, and a processing monitor element having substantially the same structure as the magnetoresistive elements on a portion of the lower gap layer where the lower shielding layer is not formed, so that these elements are arranged in a line.
The present invention further provides a method of manufacturing a substrate comprising magnetoresistive elements, the method comprising the steps of forming a lower shielding layer on the substrate and then forming an insulating layer on a portion of the substrate on which the lower shielding layer is not formed; grinding the surfaces of the insulating layer and the lower shielding layer to form the surfaces of the insulating layer and the lower shielding layer in the same plane; forming a lower gap layer on the lower shielding layer and the insulating layer; and
forming a plurality of magnetoresistive elements each comprising a multilayer film exhibiting the magnetoresistive effect and electrode layers conducting to the multilayer film on a portion of the lower gap layer where the lower shielding layer is formed, and a processing monitor element having substantially the same structure as the magnetoresistive elements on a portion of the lower gap layer where the insulating layer is formed, so that these elements are arranged in a line.
The present invention further provides a method of manufacturing a substrate comprising magnetoresistive elements, the method comprising the steps of forming an upper gap layer on magnetoresistive elements and a monitor element which are formed on a lower gap layer; forming an upper shielding layer on a portion of the upper gap layer, which is formed on the magnetoresistive elements, without forming the upper shielding layer on a portion of the gap layer which is formed on the monitor element; forming a write gap layer on the upper shielding layer and the upper gap layer on which the upper shield layer is not formed; and forming a coil layer and an upper core layer on a portion the write gap layer where the upper shielding layer is formed.
The present invention further provides a method of processing the above-described substrate comprising magnetoresistive elements, the method comprising grinding the magnetoresistive elements and a monitor element from the ABS side in the height direction while measuring the direct-current resistance value between the electrode layers of the monitor element until a predetermined direct-current resistance value is obtained.
A magnetic head slider comprising a magnetoresistive element composed of a spin valve film (a GMR element) is formed, by various kinds of processing, from a wafer in which a plurality of magnetoresistive elements are formed.
The exposed surface of the magnetoresistive element formed in the slider is referred to as xe2x80x9cthe ABS sidexe2x80x9d, which is opposed to a recording medium in reproducing signals from the recording medium. The direction perpendicular to the ABS side opposed to the recording medium, i.e., the direction away from the recording medium, is referred to as xe2x80x9cthe height directionxe2x80x9d. The length of the magnetoresistive element in the height direction is a very important dimension for determining the direct-current resistance of the magnetoresistive element.
In order to set the length of the magnetoresistive element in the height direction to a predetermined dimension by grinding (height setting processing) on the basis of the relation to the direct-current resistance, a monitor element having the same structure of the magnetoresistive element is formed in alignment with magnetoresistive elements formed on the substrate, and the ABS side of the magnetoresistive elements and the monitor element is subjected to height setting processing, while measuring the direct-current of the monitor element. At the time the predetermined direct-current resistance is obtained, height setting processing is finished to form the magnetoresistive elements each having a length in the height direction with the predetermined direct-current resistance.
However, at present, the thickness of each of the gap layers formed on and below the monitor layer decreases as the recording density increases, and thus smearing (sag) occurs in the shielding layers formed on and below the gap layers to be exposed from the ABS side in height setting processing. There is thus the problem of causing a short circuit between the monitor element and the shielding layers on the ABS side during measurement of direct-current resistance.
Particularly, in height setting processing, the ABS side of the monitor element is ground in the direction from the lower shielding layer formed below the monitor element to the upper shielding layer formed on the monitor element, and the thickness of the lower gap layer formed below the monitor element is actually smaller than the thickness of the upper gap layer formed above the monitor element.
Therefore, smearing in the lower shielding layer causes the great problem of readily producing electrical connection between the lower shielding layer and the monitor element on the ABS side.
Accordingly, in the present invention, the lower shielding layer conventionally formed below the monitor element is removed to appropriately prevent a short circuit in the monitor element during height setting processing. More preferably, the upper shielding layer conventionally formed on the monitor element is also removed.
Besides the lower gap layer and the upper gap layer, insulating layers are preferably formed on and below the monitor element with no shielding layer formed.